Variable resistance



Dec. 23, 1930. LAUTER 1,785,779

VARIABLE RESI STANCE Filed Nov. 10 1928 ATTORNEY Patented Dec. 23, 1930 UNITED STATES PHILIP LAUTER, OF NEW YORK, N. Y.

VARIABLE RESISTANCE Application filed November 10, 1928. Serial No. 318,562.

This invention relates to a variable resistance, and an object of the invention is to provide means whereby an unusually long resistance element may be operatively mounted upon a carrying base of a given size, and to provide a contact element movable to any selected point along the length of said resistance element.

It has heretofore been customary in resistance elements of the type with which this invention is concerned to provide aresistance element in circular form upon one surface of a small disc of insulating material, and to provide a central shaft with a contact arm arranged to sweep around the resistance element, the resistance element being at all points equi-distant radially from the shaft and being of a length less than a complete circle, one end of the resistance element being connected with one side of a source of electrical energy, the opposite side of the source being in the shaft and contact arm so that by movin the arm along the resistance element, away rom the current carrying end of the resistance element, more or less resistance will be thrown into the circuit according to the distance to which the arm is moved. According to this arrangement the -full amount of resistance has been thrown into the circuit when the arm has traversed less than a full circle.

By the present improvement it is made possible to require any desired number of complete revolutions of the contact arm in order to reach the point of maximum resistance. The degree of increase for a given movement of the arm is made correspondingly less, and hence greater accuracy may be readily attained. In instances where the resistance ele- 40 ment consists of the usual coil ofresistance wire with the contact arm sweeping or jumping along from convolution to convolution the degree of change in each convolution may be materially reduced by the use of wire having greater conductivity, or otherwise.

A specific object of the present improvement accordingly is to provide means whereby the resistance element may extend in a generally circular path along the surfaceof its carrying base for adistance more than a complete circle, and to provide a contact arm movable at will to any selected point along the length of such resistance element.

A further specific object is to provide means efiective to guide the contact arm for maintaining it alwaysin proper contact with the resistance element irrespective of its position lengthwise of said element. i i

A further and specific object is toprovide a resistance element arranged in convolute form, to provide the contact arm with a brush or finger portion for contacting with the resistance element, and to provide means whereby the carrying base will constitute a guide for always maintaining the brush in proper register with the resistance element.

Other objects and aims of the invention, more or less specific than those referred to above, will be in ,part obvious and in part pointed out in the course of the following 7 description of the elements, combinations, arrangements of parts and'applications of principles constituting the invention; and the scope of protection contemplated will be indicated in the appended claim.

In the accompanying drawings-which are to be taken as a part of this specification, and in which I have shown merely a preferred form of embodiment of the invention:--

Fig. 1 is a top plan view of a variable resistance device constructed in accordance with this invention. v

Fig. 2 is a. transverse sectional view taken. substantially upon the plane of line II--II 85 of Fig. 1.

Fig. 3 is a fragmentary sectional'view illustrating a portion of the carrying base provided with a modified form of resistance element therein.

Fig. 4 is a fragmentary detail viewof the resistance element appearing in Fig. 3.

Fig. 5 is a view similar to Fig. 3 but illustrating a modified arrangement of the resistance element with respect to its carrying95 base, and

Fig. 6 is a fragmentary sectional view taken upon the plane of line VIVI of. Fig. 5. I

Referring to the drawings for describing 100 in detail the structure illustrated therein, the reference character L indicates the carrying base. This is of insulating material and is preferably in the form of a small disc substantially as indicated. At its centre is an aperture 1 within which is fitted a sleeve 2 forming a bearin within which is loosely received an operating shaft 3 for the contact arm G.

A suitable control handle or knob as H is provided upon the shaft 3 by which to rotate it manually at will. In practice the arm G is usually arran ed at one side of the disc while the knob 1% is at the opposite side, the shaft being adapted to extend through a panel board or other element as 4 in the usual manner common to radio set construction.

The contact arm G projects radially from the shaft across the surface of the d1sc and carries thereon a contact finger 5 for rubbing against the resistance element 6 carried by the disc. The resistance element 6 is arranged at the bottom of a groove 7 which extends in a convolute or spiral path about the shaft 3 and which may be of a length sufiicient to make any desired number of complete convolutions about said shaft. Between each convolution the base L provides a partition as 8 effectively separating the respective convolutions, and the opposing walls as 9 and 10 of the groove constitute guide surfaces for engagement by the contact finger 5 to cause the contact finger to always follow the groove.

The contact finger 5 is connected with the arm G in such manner that it projects into the groove betweenthe walls 9 and 10 and will always be free to follow the groove under the guidance of said walls 9 and 10. In the instance illustrated the contact finger is shown as being slidably mounted upon said arm so that it can move at will to any point along the length of the arm as may be determined by the walls 9 and 10 when the arm is swung by means of the shaft 3. The arm G is preferably of rectangular cross section and the contact finger has a cross head portion as 11 having a similarly shaped aperture as 12 loosely receiving the arm so that the finger will be held against rotary movement about the arm at all times.

As a convenient means of insuring spring pressure of the contact finger against the resistance element at all times the drawing herewith shows said finger as being supplied with a friction ball as 13 therein spring pressed, as by a spring 14 arranged within the finger, against the resistance element.

In the structure Figs. 1 and 2 the resistance element is shown as being in the form of a paint or moulded compound applied in the bottom of the groove.

In the modification Figs. 3 and 4 the resistance element is shown as being in the form of a coil of wire as 15, wound upon a flexible core 16 and placed in the bottom of the groove.

In the modification Figs. 5 and 6 the resistance element instead of being arranged in the bottom of the groove is shown as being applied upon the fiat surface of the disc, for instance upon the outer surface of the partition 8. In this instance the contact finger is in two separate parts, one part as 17 being resilient and bearing upon the resistance element thereby constituting the contact finger proper, and the other part consisting of a lug like projection as 18 extending into the groove? for being guided by the walls of said groove in the same manner as before.

A terminal member as 19 is shown as extending from one end of the resistance element while the opposite terminal is shown as comprising a binding post or the like as 20 upon the shaft 3.

A cover member as 21 may be employed for covering and protecting the contact arm and resistance element if desired.

It will be seen that by the structure herein suggested the resistance element upon a given size of carrying base may be of any desired length within reason. The maximum resistance may be thrown into the circuit after any desired number of revolutions of the knob H accordingly. A given amount of rotary movement of the contact arm may be made to produce a very considerably less variation in the resistance as compared with the variation heretofore produced where the complete resistance element is necessarily less than a single circle, and hence much greater accuracy of adjustment may be readily attained.

It will of course be understood that any desired maximum amount of resistance may be provided for by this device merely by adding convolutions to the len h thereof. If one or two convolutions o resistance material are insufficient to furnish the desired maximum it is simply a matter of adding length in the form af added convolutions about the central shaft 3.

This marked improvement is secured without increase in size of the device, and without appreciable increase in cost of manufacture.

As many changes could be made in this construction without departin from the scope of the invention, as de ned in the following claim, it is intended that all matter contained in the above description or shown in the accompanying drawings, shall be interpreted as illustrative only and not in a limiting sense.

Having thus described my invention, what I claim is new and desire to secure by Letters Patent is 2- In a variable resistance device, in combination, a carrying base having an aperture therethrough, a shaft projecting through said aperture, an arm extending radially from said shaft adapted to be moved by said shaft rotatably about the surface of said base, 5 said base having a groove in its surface extending in a spiral direction about said shaft, a length of resistance material arranged at the bottom of said groove extending longitudinally along the length of the groove and thus in a spiral direction about said shaft, a contact finger carried by said arm non-rotatably mounted thereon but slidably movable longitudinally thereof toward and away from the shaft, said contact finger consisting of a hollow tubular member arranged to extend laterally from the arm lengthwise into the groove so that the outer wall surfaces of said member have co-operative engagement with the walls of the grove to cause said member to follow the groove and slide along the arm during movement of the arm by the shaft, and a separate spring pressed contact forming element arranged in the hollow of said member in electrical connection therewith and projecting therefrom into engagement with saidresistance mate rial.

In testimony whereof I afiix my signature. v PHILIP LAUIER. 

